1. Field of the Invention
The present invention relates to a storage apparatus, or more particularly, to a storage apparatus having a carriage for reading or writing data from or on a storage medium. The storage apparatus offers improved precision in positioning a carriage relative to a storage medium because the resonant frequency of the coils for driving the carriage is high.
2. Description of the Related Art
Storage apparatus having a carriage for reading or writing data from or on a storage medium include a magneto-optical disk (hereinafter, simply, an optical disk) drive. The optical disk drive has an optical system. The optical system irradiates light emanating from a laser diode onto an optical disk that is a recording medium so that data can be recorded on the optical disk. The optical system is used to detect data in light returned from the optical disk so as to read information recorded on the optical disk. The optical system in the optical disk drive consists of a stationary optical system including a laser diode and a sensor for detecting returned light, and a movable optical system for irradiating a light beam sent from the stationary optical system to a desired track on the optical disk.
The movable optical system includes a mirror, an objective, and a carriage. The mirror changes the path of a light beam traveling from the stationary optical system towards the optical disk. The objective narrows the light beam and irradiates it onto a desired track on the optical disk. The carriage has a mechanism for focusing the objective. The carriage is movable along rails laid down in a radial direction of the optical disk, and moved along the rails when driven by a rectilinear voice coil motor.
However, in the conventional movable optical system, driving coils may resonate at a low frequency due to current flowing into the driving coils. Consequently, a frequency band in which a carriage positioning control system is actuated cannot be raised, and precision in positioning cannot be maintained. There is therefore an increasing demand for a carriage for an optical disk drive structured so that driving coils mounted on both flanks of the carriage will not resonate and the carriage can be positioned very precisely.
The movable optical system included in the conventional optical disk drive has the carriage capable of sliding along two support rails below the optical disk and movable in radial directions of an optical disk. Slide bearings are incorporated in the carriage so that the carriage can smoothly slide along the support rails. Moreover, a reflector mirror is included in a carriage body. An objective is located above the reflector mirror while supported by a support spring. The objective is driven by objective driving magnetic circuits. A light beam traveling from the stationary optical system located on an extension of a moving range within which the carriage is moved is focused on the optical disk.
Carriage driving coils each shaped like a parallelepiped are mounted on both flanks of a carriage body. A magnetic circuit composed of a first yoke having a permanent magnet and a second yoke penetrating through the driving coil is formed around each driving coil.
In the conventional optical disk drive, the driving coils are structured to be long in the direction of movement in which the carriage moves and in a direction perpendicular to the direction of movement, and to be short and flat in a direction perpendicular to the surface of the optical disk. The magnetic circuits are used to induce magnetic fields in the direction perpendicular to the surface of the optical disk. A driving force is generated in the carriage due to the Lorentz force exerted due to coil currents flowing through the driving coils and in the magnetic fields.
However, in the conventional optical disk drive, the driving coils resonate at a low frequency (5 to 6 kHz) to vibrate vertically relative to the flanks of the carriage body. Moreover, the driving coils resonate at a low frequency (5 to 6 kHz) to vibrate back and forth relative to the flanks of the carriage body. In the conventional optical disk drive, a frequency band in which a carriage positioning control system is actuated cannot be raised. This poses a problem in that precision in controlling the positioning of the carriage cannot be improved.
An object of the present invention is to provide a storage apparatus such as an optical disk drive structured to be able to raise the resonant frequency of carriage driving coils and to maintain excellent precision in positioning a carriage.
To accomplish the above object, the present invention provides a storage apparatus having support rails laid down on a plane opposed to a storage medium in a direction transverse to the tracks on the storage medium. The storage apparatus uses a carriage movable along the support rails to access the storage medium. The carriage is moved using driving coils mounted on the flanks of the carriage and magnetic circuits each composed of a permanent magnet and yokes. The driving coils are each shaped like a parallelepiped whose sides extending along the flanks of the carriage are longer than other sides extending perpendicular to the flanks of the carriage. The permanent magnet or yokes of each magnetic circuit is opposed to the plane of each parallelepiped-shaped driving coil containing the long sides.
If the length of the sides of each parallelepiped-shaped driving coil extending along the flank of the carriage is 1 and the length of the sides thereof extending perpendicular to the flank may be set to fall within 0.55 to 0.65, the rigidity of the driving coils can be improved.
Moreover, support members may be located on and under the driving coils mounted on the flanks of the carriage and thus hold the driving coils while clamping the tops and bottoms of the driving coils.
The edges of a support member on the opposite sides of each driving coil may be extended to clamp the thick portion of the driving coil on the opposite sides. Inclusion of the support members and extension of the edges of the support members lead to improvement in the rigidity of the driving coils. Moreover, a magnetic body to be attracted by the permanent magnet in the adjacent magnetic circuit may be attached to the distal ends of support members.
When the magnetic body is attached to the distal ends of support members, even if the magnetic disk drive may entirely be excited and the carriage may be accelerated, the carriage remains in contact with the rails on a stable basis. It will not take place that the carriage floats above the rails and it does not vibrate.
In addition, a reinforcement plate for linking the bottoms of the two driving coils mounted on the flanks of the carriage may be attached to the carriage.
Furthermore, ribs may be formed on the reinforcement plate.
When the reinforcement plate is attached to the carriage, the carriage is reinforced on the side of the bottom thereof. Resonance hardly occurs at a low frequency. When the ribs are formed on the reinforcement plate, the rigidity of the reinforcement plate will be further improved.
The reinforcement plate may be used to hold a flexible printed-circuit board for supplying power to electrical parts included in the carriage. In this case, the reinforcement plate acts as a holder for supporting the flexible printed-circuit board and preventing interference of the flexible printed-circuit board with other parts.
The weight of the reinforcement plate may be determined so that the center of gravity of the carriage having the reinforcement plate attached thereto will be aligned with a point at which a driving force exerted by the driving coils is applied to the carriage, in a direction of movement in which the carriage is moved. In this case, the carriage body having the reinforcement plate attached thereto can be moved smoothly in the radial direction of an optical disk.
If the reinforcement plate is made of a nonmagnetic material, the reinforcement plate will not be susceptible to the magnetic circuits.